Data in the literature has consistently shown that there is not only significant inherent contrast in the[unreadable] electrical bioimpedance of normal and neoplastic breast tissue but also that spectroscopic response can[unreadable] provide important functional information. Further, efforts to develop tomographic imaging systems based on[unreadable] electrical impedance have matured to the point where many of its basic principles and practices are well[unreadable] understood. Project II, Electrical Impedance Spectroscopy and Imaging (EIS), has exploited this foundation[unreadable] to target identification of the most promising roles for EIS imaging in the setting of clinical breast care.[unreadable] During the current funding period, it has completed an ambitious effort to construct, deploy and initially[unreadable] evaluate an ultra-fast, multi-channel, multi-frequency imaging system capable of delivering a volumetric[unreadable] breast exam safely, comfortably and efficiently. The system and its prior prototypes have been used in well[unreadable] over 100 clinical sessions in order to (i) establish exam consistency, (ii) identify normative responses in[unreadable] breasts without disease, (iii) explore electrical property variations due to hormonal changes during the[unreadable] menstrual cycle and (iv) evaluate the detection and characterization of screening abnormalities. The driving[unreadable] force for Project II renewal is optimization, validation and thorough evaluation of the most recently installed[unreadable] EIS imaging system which is, by far, the most advanced version of the instrument that is expected to[unreadable] improve considerably the prior encouraging results. The specific aims for continuation include (1) data[unreadable] acquisition and breast interface optimization of electrode density, geometry, and registration for three-dimensional,[unreadable] high frequency EIS breast imaging, (2) software optimization for ultrafast frame-rates, multi-tone[unreadable] testing, virtual current drive along with three-dimensional high frequency image reconstruction, (3)[unreadable] development, validation and utilization of a probe-based measurement system suitable for studies of EIS-imaged[unreadable] breast tissues at the time of surgical resection, and (4) participation in clinical studies conducted[unreadable] through the Clinical Core which target screening abnormalities recommended for biopsy, palpable masses[unreadable] on clinical breast exams and locally-advanced cancers receiving neoadjuvant therapy. If successful, it is[unreadable] expected that these aims will generate sufficient evidence to allow convincing estimates of the potential of[unreadable] EIS breast imaging as an alternative for differential diagnosis and pilot data in support of a role in treatment[unreadable] prognosis and therapy monitoring to be made which would inform decisions on the initiation of multi-center[unreadable] trials with the technology in the future.